iTextSharp–Add watermark to PDF

public class PdfWriterEvents : IPdfPageEvent
   {
       string watermarkText = string.Empty;
 
       public PdfWriterEvents(string watermark)
       {
           watermarkText = watermark;
       }
       public void OnStartPage(PdfWriter writer, Document document)
       {
           float fontSize = 80;
           float xPosition = iTextSharp.text.PageSize.A4.Width / 2;
           float yPosition = (iTextSharp.text.PageSize.A4.Height - 140f) / 2;
           float angle = 45;
           try
           {
               PdfContentByte under = writer.DirectContentUnder;
               BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);
               under.BeginText();
               under.SetColorFill(BaseColor.LIGHT_GRAY);
               under.SetFontAndSize(baseFont, fontSize);
               under.ShowTextAligned(PdfContentByte.ALIGN_CENTER, watermarkText, xPosition, yPosition, angle);
               under.EndText();
           }
           catch (Exception ex)
           {
               Console.Error.WriteLine(ex.Message);
           }
       }
       public void OnEndPage(PdfWriter writer, Document document) { }
       public void OnParagraph(PdfWriter writer, Document document, float paragraphPosition) { }
       public void OnParagraphEnd(PdfWriter writer, Document document, float paragraphPosition) { }
       public void OnChapter(PdfWriter writer, Document document, float paragraphPosition, Paragraph title) { }
       public void OnChapterEnd(PdfWriter writer, Document document, float paragraphPosition) { }
       public void OnSection(PdfWriter writer, Document document, float paragraphPosition, int depth, Paragraph title) { }
       public void OnSectionEnd(PdfWriter writer, Document document, float paragraphPosition) { }
       public void OnGenericTag(PdfWriter writer, Document document, Rectangle rect, String text) { }
       public void OnOpenDocument(PdfWriter writer, Document document) { }
       public void OnCloseDocument(PdfWriter writer, Document document) { }
   }

Now we can use this class in pdf building Class~ following way to show watermark on your pdf document

  using (MemoryStream msReport = new MemoryStream())
            {

        //WaterMark
                PdfWriter pdfWriter = PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
                pdfWriter.PageEvent = new PdfWriterEvents("Demo Document");

 

                pdfDoc.Open();
                //Adding Image
                pdfDoc.Add(jpg);
                //Adding heading
                pdfDoc.Add(heading);
                //Adding heading Description
                pdfDoc.Add(headingdesc);

                //Adding Table
                pdfDoc.Add(table);

                pdfDoc.Add(employeeSignature);

                pdfDoc.Add(employeeSignaturePart2);

                pdfDoc.Close();

                Response.Write(pdfDoc);

                Response.End();
            }
        }

The Follwing is How it Looks after adding watermark